Human evolution: cavemen’s secret

A few weeks ago, I wrote about an exciting area of neuroscience, Optogenetics, that had rapidly developed since I left college. Another area which has seen huge changes in the past few years is the study of human evolution, specifically the role played by Neanderthals in our past. In the typical picture of evolution, the Neanderthal is often depicted as a caveman holding a large stick. Neanderthals were our closest relatives and have been extinct for about 30,000 years. They lived in Europe from 200,000 years ago until their extinction. Last year, the complete Neanderthal genome was sequenced so how will this advance our understanding of human evolution and will we finally discover what makes us human?

A group of scientists from Germany and the United States got together and set up the Neanderthal Genome Project. Neanderthal’s share 99.5% of our DNA and hide many secrets of our evolution. To put this in context, we share 94% of our DNA with chimps, our closest living relative. Ancient DNA was obtained from Neanderthal bones from Croatia and carefully sequenced. Since the DNA from their bones is so similar to human DNA, scientists had to make sure they did not contaminate the samples.  As DNA can be obtained from any cell in the body, a DNA-free lab is particularly hard to create.

A lot of information is hidden within Neanderthal DNA. The most surprising discovery was that Neanderthals may have interbred with modern humans with modern humans as they spread from Africa 100,000 years ago. Apart from having a different shaped brain and being a bit heavier, Neanderthals weren’t much different in appearance from us. This similarity may have led to interbreeding between modern humans and their cavemen ancestors in the Middle East. Fossil evidence places them both in similar areas during the same period but this discovery has caused controversy in the scientific community.

Mating between the two species, could have resulted in a hybrid advantage in humans i.e. perform better than their original species. An example of this was demonstrated in new research which was published yesterday. This proposed that Neanderthals may have passed on  a variety of immune system genes called HLA-A, HLA-B and HLA-C to humans. These genes help fight virus and bacterial infections. More research is needed before this is proven as another possibility is that these genes evolved independently in both species.

We can learn a lot in other ways from our closest relative’s DNA. Comparisons between human and Neanderthal DNA can lead us to discover what makes us uniquely human.  For instance, lactose tolerance, which is the ability to digest milk past infancy, does not occur in Neanderthals but is present in many Europeans. This shows that this ability occurred recently in our past. A trait that is present in both Neanderthals and modern humans is language ability so this occurred in our more distant past.

There are many secrets just waiting to be revealed in Neanderthal’s DNA. Differences between us and these cavemen may shed light on what led to their extinction and our success. A new piece of the evolutionary puzzle can completely change the overall picture of the origin of our species. As we discover more pieces, this picture will continue to change and evolve. There are lots of exciting research in this area to look forward to in the near future… yabba dabba doo!

ResearchBlogging.orgAbi-Rached L, Jobin MJ, Kulkarni S, McWhinnie A, Dalva K, Gragert L, Babrzadeh F, Gharizadeh B, Luo M, Plummer FA, Kimani J, Carrington M, Middleton D, Rajalingam R, Beksac M, Marsh SG, Maiers M, Guethlein LA, Tavoularis S, Little AM, Green RE, Norman PJ, & Parham P (2011). The shaping of modern human immune systems by multiregional admixture with archaic humans. Science (New York, N.Y.), 334 (6052), 89-94 PMID: 21868630

Top image: Max Planck Institute / Wikimedia Commons

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